You can get a replacement EPROM chip from dealer for the 561 ( i belie e one is also available for the 951) for about $100-120 (local dealer price, Borton may have them cheaper, I got one through Trollhattan for about $68 last year.)

When I was checking with dealer parts dept. they told me that the chip is the weak link that gives out and when they rebuild them , all they do is replace the chip, (unless the board is visibly burned in which case they trash it, bad core)
The replacement chip for the 561 upgrades to the latest emission control and fuel efficiency standards, and starts beter when cold ( I alkso noticed smoother accelleration and more pick up climbing hills )
Takes about ten minuits , and an anti-static wrist strap and large chip puller ( available from radio shack)